Electric converting apparatus



Nov. 11, 1941. A, J LARRECQ ELECTRIQ CONVERTING APPARATUS Filed Sept.22, 1939 .n. M M

Inventor:

His Attorney.

c e r r a L J W O m n A Patented Nov. 11, 1941 2,262,505 ELECTRICCONVERTING APPARATUS Anthony J. Larrecq,

New York Beach Bluflf, Mass, assignor to General Electric Company,

a corporation of Application September 22, 1939, Serial No. 296,076

15 Claims.

My invention relates to electric valves and electric convertingapparatus, and more particularly to those types of valves in which anarc is periodically ignited and extinguished between a plurality ofelectrodes and a continuous flow of some fluid medium is maintainedbetween the electrodes.

Electric converting apparatus of the kind referred to have beendescribed in a book by Erwin Marx, entitled "Lichtbogenstromrichter,published in Berlin in 1932, and in United States Letters Patent No.2,074,930, granted March 23, 1937, upon an application of Erwin Marx. Insuch apparatus it has been customary to provide a continuous flow ofgas, such as air, within the gaps between the electrodes. However, dueto the action of oxygen in the air the main electrodes of the prior artdevices are subject to considerable deterioration and therefore it hasbeen proposed to use a relatively inert gas instead of air. However,even with the use of such inert gas deterioration of the electrodes isconsiderable and hence it would be desirable to provide a valve of thegas cooled arc type wherein less burning and deterioration of theelectrodes occur. In the arrangements of the prior art it has beennecessary to provide an auxiliary electrode which serves as a startingor ignition electrode. In order that this auxiliary electrode may causethe arc discharge to start between the main electrodes considerableauxiliary equipment is necessary. It would be desirable to provide avalve of the gas cooled arc type wherein the auxiliary equipmentheretofore required for igniting the arc discharge may be dispensed withalong with the'difiiculties encountered in the operation of suchauxiliary equipment. Also in some of the arrangements of the gas cooledarc type of electric valves difficulties have been incurred inextinguishing the arc at the end of the conducting period, i. e., atcurrent zero. In accordance with my invention therefore, I provide anarrangement wherein heretofore necessary auxiliary equipment may bedispensed with, wherein a minimum deterioration of the electrodesoccurs, and wherein the extinguishment of the are at the proper tim ismuch more positive and satisfactory than with apparatus heretofore used.

It is an object of my invention to overcome the disadvantages abovenoted in connection with valves of the gas cooled arc type and toprovide a more efficient and more positive valve for use in connectionwith electric converting apparatus.

It is another object of my invention to provide a new and improvedelectric valve for use in connection with an electric convertingapparatus.

Still another object of my invention is to provide an electric valveapparatus including valves of the gas cooled arc type wherein lessdeteriora tion of the electrodes occurs and whereby more efiicient andmore stable operation is obtained.

It is a further object of my invention to provide an electric valveconverting apparatus including valves of the gas cooled arc type whereincomplicated auxiliary apparatus for initiating the arc discharge atperiodic intervals is eliminated and wherein suitable means are providedfor extinguishing the are at the end of the conducting period.

In accordance with the illustrated embodiment of my invention I providefor an electric converting apparatus an electric valve or electricvalves of the gas cooled arc type comprising a plurality of stationarysegmental electrodes annularly arranged, connected to the respectivephases of the alternating current circuit, while an annular collectorring is suitably spaced from said segmental electrodes so as to producean arc discharge gap therebetween. A segmental conducting member isrotated in synchronism with the alternating current circuit in the arcdischarge gap, so reducing this gap that an arc discharge may readily beinitiated between one of the segmental electrodes and the collectorring. The rotating conducting member is so dimensioned as to reduce thearc gap only between one segmental electrode at a time and currentflowing through the arc discharge is caused to commutate from onesegmental electrode to another by the great increase in the arc gap aswell as by cooperation of a gas blast which sweeps past the segmentalfaces causing the arc to move thereacross and to commutate from segmentto segment at the proper'time. This gas blast is produced by fan meansmounted on the rotating member.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, Will best be understood by reference to the followingdescription taken in connection with the accompanying drawing in whichFig. 1 is a cross sectional view of one form of my gas cooled arc typeof valve; Fig. 2 discloses the stationary segmental electrodes shown incross section in Fig. l; 3 illustrates the rotating member and fanblades shown in cross section in Fig. 1; Fig. 4 discloses the stationaryannular direct current collector ring shown in cross section in Fig. 1,and Fig. bis 9. diagrammatical representation of one form of convertingapparatus employing my new gas cooled arc type of valve. Referring tothe drawing I have shown in Fig. 1 one form of my gas cooled arc typeofvalve l including a sealed casing ll mounted on a suitable support l2which should preferably be constructed of insulating material so thatthe apparatus may be used for high voltage installations. Mounted withinthe sealed casing I l are a plurality of segmental electrodes l3annularly arranged as best shown in Fig. 2 and lodged in a suitabledielectric or insulating material l4 in such a manner that the segmentalfaces are flush with the surface of the dielectric l4 so as to permit asmooth path for cooling medium as will be described hereinafter.Although I have shown in Fig. 2 six segmental faces it will beunderstood by those skilled in the art that there should be as manysegmental faces as there are alternating current phases in theconverting system with which this electric valve is to be used. Thesegmental electrodes l3 and dielectric l4 are fixedly supported withinthe sealed casing H by means of an annular support l5. Similarly mountedin the opposite end of sealed casing H is a direct current collectorring or electrode l'6 of annular shape also suitably lodged in adielectric or insulating material I! so that the collectorring I6 isflush with the surfaces of, the insulating material thereby to provide asmooth path for the cooling medium as will be described hereinafter. Thedirect current collector ring I6 is best shown in Fig. 4. This collectorring l6 and insulating material I! are fixedly supported within casingII by means of annular support ill in such a manner as to provide arelatively large gap or space between segmental electrodes l3 andcollector ring l6, and a rotor l9, shown also in Fig. 3, is mounted soas to rotate within the gap formed therebetween. The rotor I9 isintegrally mounted or otherwise suitably secured upon a hollow shaft andadapted to rotate with the shaft 20 which is provided with suitablebearings 2| and 22. A synchronous motor 23 drivingly connected to shaft20 and rotor I9 is preferably mounted directly to casing ll so as toform an integral unit therewith. Rotor I9 is provided with an enlargedsegmental portion 24 of approximately the same circumferentialdimensions as segmental electrodes l3 so as to reduce the gap betweensuccessive segmental electrodes l3 and collector ring It to a minimum.Segmental electrodes I 3, enlarged portion 24 of rotor l9 and collectorring l6 are constructed of any suitable conducting material, although inorder to reduce deterioration I prefer to use electrodes constructed ofa eutectic silver-copper alloy' to which has been added a small amountof thorium or barium similar to the electrodes disclosed and broadlyclaimed in U. S. Letters Patent No. 2,151,567, granted March 21, 1939,upon an application of Hugo J. Seemann, and assigned to the assignee ofthe present application. Enlarged segmental portion 24 thus produces tworelatively short gaps and 26, gap 25 being formed between one ofsegmentalelectrodes l3 and enlarged segment 24 of rotor l9 and gap 26being formed between collector ring l6 and en larged segment 24 of rotorl9. Gaps 25 and 26 are sufliciently small so that an arc dischargemayreadily be initiated thereacross and further the arc losses arereduced to a minimum by constructing gaps 25 and 26 as small as possibledetermined by the necessary minimum running clearance. The remainingportion of rotor l9 to rotate.

has a very narrow cross section so that the gap between the remainingsegmental electrodes I 3, not adjacent enlarged portion 24 of rotor l9,and collector ring [6 is suiiiciently large to prevent an arc dischargefrom being initiated thereacross and hence also reducing the likelihoodof arc backs. By means of synchronous motor 23 rotor I9 is rotatedatsynchronous speed in the gap between segmental electrodes l3 andcollector ring l6 and the enlarged segment 24 is always opposite theparticular segmental electrode l'3 through which current is to beconducted, by means of arc discharges in gaps 25 and 26, at thatparticular instant. This current is commutated from one segmentalelectrode l3 to another as the enlarged portion 24 of rotor l9 continuesAlthough I have illustrated segmental electrodes I 3, and collector ring[6 .as fixedly mounted while member 19 is rotatable, it will beunderstood by those skilled in the art that all that is necessary is arelative movement between these members and it is immaterial as far asmy invention is concerned as to how this relative movement is obtained.A plurality of fan blades 21 are provided on rotor l9 so as to circulatea cooling medium through gaps 25 and 26 as well as through therelatively large gap formed between segmental electrodes l3 andcollector ring Hi. This cooling medium not only cools the electrodes butalso serves to move the arc foot-point diagonally across the segmentalfaces of electrodes I3. The clearance between fan blades 21 andinsulating members l4 and I! should be' reduced to a minimum and it maybe preferable to employ labyrinth packing arrangements similar to thoseused for interstage turbine packing. A plurality of heat transfersurfaces or cooling tubes 28 are provided to cool the fluid medium whichleaves the arc discharge gaps 25 and 26. The fluid medium may becontinuously recirculated in a closed system by passing through openings29 and 30 in annular supporting members f5 and I 3, respectively. If aclosed system is employed the fluid cooling medium will be continuallyrecirculated and cooled by contact with heat transfer members 28. Itwill, of course, be understood by those skilled in the art, that thepressure of the fluid cooling medium may be suitably chosen as well asthe particular type of medium. The particular fluid medium used and thepressure thereof are not critical so far as my invention is concernedand any suitable medium such as air or nitrogen may be used, although Iwould prefer to use one of the inert gases such as argon in case aclosed system is employed. In Fig. 1, however, I have shown anarrangement wherein a cooling fluid circulating system is not completelyenclosed in casing II, but where an additional supply of cooling mediumis provided through hollow shaft 20 and openings 3| therein. Thepressure of this cooling, medium may be controlled by any suitable means(not shown). It will, of course, be understood by those skilled in theart, that if openings 3| in hollow shaft 29 were eliminated then theclosed type of system would be provided. Heat transfer members 28 mayhave any suitable cooling fluid circulated therethrough such as water orair and in certain cases a suitable refrigerant might even be used.

In Fig. 5 I have diagrammatically shown my gas cooled arc type of valveas applied to an electric converting apparatus. It will be understoodthat my invention is applicable to any electric converting system wellknown in the art and it is equally adapted to rectification ofalternating current or inversion of direct current. For simplicity ofdisclosure I have shown in Fig. 5 my invention as employed in connectionwith a six-phase rectifier circuit wherein electrical energy istransmitted from a three-phase alternating current circuit 33 to directcurrent circuit 34. A transformer 35 is provided having a deltaconnected primary winding 36 associated with alternating current circuit33 and a six-phase star connected secondary winding 31, the respectivephases of which are directely connected to one of the segmentalelectrodes l3. The neutral terminal of star connected secondary winding31 is connected to the negative terminal of the direct current circuit,while the positive terminal of the direct current circuit is connectedto collector ring IS.

The operation of the illustrated embodiment of my invention will best beunderstood by reference to Fig. 5. Rotor I9 is rotated by means ofsynchronous motor 23 in synchronism with and in proper phaserelationship to alternating current circuit 33 from which synchronousmotor 23 is preferably energized. Enlarged section 24 of rotor I9 is soadjusted as to come opposite successive segmental electrodes l3 whichhave for the particular instant a positive potential applied theretofrom alternating current; circuit 33 of such a value as to exceed thethreshold value of voltage required to initiate an arc discharge acrossgaps 25 and 26. Each segmental electrode l3 conducts current forsubstantially sixty electrical degrees after which the succeedingelectrode becomes conductive. This happens when the next successivesegmental electrode has a sufiiciently positive potential appliedthereto to exceed the threshold voltage required to initiate an arcdischarge across gaps 25 and 26 for at this instant enlarged portion 24of rotor I9 has L reached a position such that its leading edge justoverlaps the end of the succeeding electrode. Hence the arc discharge iscaused to commutate from one segmental electrode l3 to another partly bythe large increase in arc gap which obtains as soon as the trailing edgeof enlarged segment 24 has passed the end of the particular segmentalelectrode which was conducting current and also because of the blast ofcooling medium produced by fan blades 21 which causes the arcfoot-points 5 to move diagonally across the segmental faces ofelectrodes l3. Of course, due to the relative movement of the stationaryand rotating segmental electrode the arc foot-points naturally tend tomove over the face of the same. The large increase in gap is such as topractically eliminate the possibility of arc backs when the high inversevoltage appears across the particular segmental electrode which has justbecome nonconductive. Furthermore the potential of the segmentalelectrode [3 which is conducting ourrent varies during the arc dischargeso as to produce a minimum potential difference at the instant the arcis being extinguished. The proper phase relationship of rotor l9 and thealternating potentials impressed on segmental electrodes I3 ismaintained by suitable adjustment of the synchronous motor field, thisadjustment being such that the enlarged segment 24 comes opposite theproper segmental electrode 13 when the potential of the associatedalternating current phase exceeds the threshold value of potentialrequired to initiate the arc which passes cur rent from that particularelectrode to the direct current collector ring Hi. It will be understoodby those skilled in the art that my proposed arrangement is in somerespects analogous to the multi-anode, single-cathode electric dischargevalves known to the prior art.

While I have described what I at present consider the preferredembodiment of my invention, it will be obvious to those skilled in theart that various changes and modifications may be made without departingfrom my invention, and I, therefore, aim in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

' 1. In combination a supply circuit, a load circuit, one of saidcircuits being an alternating current circuit, a transformer and aconverting apparatus interconnecting said circuits, said transformerhaving one winding connected to said alternating current circuit, and aplurality of phase windings inductively associated therewith, saidconverting apparatus comprising a plurality of angularly spacedelectrodes associated with said phase windings, other electrode meansmounted in spaced relationship with each of said plurality of electrodesso as to provide a uniform gap therebetween throughout the angularextent of said plurality of electrodes, and means for transmittingelectrical energy between successive ones of said plurality ofelectrodes and said other electrode means comprising a member rotated insaid gap in synchronism with said alternating current circuit, saidmember successively reducing the gap between each of said plurality ofelectrodes and said other electrode means so as to initiate an arcdischarge between said other electrode means and each of said pluralityof electrodes in succession, said member having an extent greater thanthe distance between adjacent ones of said plurality of electrodes sothat the arc discharge is readily transferred from one of said pluralityof electrodes to the next as said member is rotated.

2. In combination a supply circuit, a load circuit, one of said circuitsbeing an alternating current circuit, a transformer and a convertingapparatus interconnecting said circuits, said transformer having onewinding connected to said alternating current circuit, and a pluralityof phase windings inductively associated therewith, said convertingapparatus comprising a plurality of electrodes associated with saidphase windings, other electrode means mounted in spaced relationshipwith each of said plurality of electrodes so as to provide a uniform gaptherebetween, and means for transmitting electrical energy betweensuccessive ones of said plurality of electrodes and said other electrodemeans comprising a member rotated in said gap in synchronism with saidalternating current circuit, said member successively reducing the gapbetween each of said plurality of electrodes and said other electrode soas to initiate an arc discharge therebetween, and means for commutatingsaid are discharge between said plurality of electrodes.

3. In combination an alternating current supply circuit, a directcurrent load circuit, a transformer and a converting apparatusinterconnecting said circuits, said transformer having a primary windingconnected to said supply circuit and a polyphase secondary winding, aplurality of stationary electrodes each connected to one of the phasesof said secondary winding, a collector ring connected to said directcurrent circuit and positioned in spaced relation to said plurality ofelectrodes and a rotary member including a conducting element mountedbetween said first mentioned electrodes and said collector ring, andmeans for driving said rotary member in synchronism with saidalternating current supply circuit so that an electrical discharge isproduced successively between each of said plurality of stationaryelectrodes, said conducting element and said collector ring, saidconducting element having an extent in the direction of the rotationgreater than the distance between adjacent ones of said plurality ofelectrodes to provide an overlap between said conducting element andadjacent ones of said electrodes as said member is rotated thereby tofacilitate the transfer of the are between said plurality of electrodes.

4. In combination an alternating current supply circuit, a directcurrent load circuit, a transformer and a converting apparatusinterconnecting said circuits, said transformer having a primary Windingconnected to said supply circuit and a polyphase secondary winding, aplurality of stationary electrodes each connected to one of the phasesof said secondary winding, a collector ring connected to said directcurrent circuit and a rotary member mounted between said first mentionedelectrodes and said collector ring, means for driving said rotary memberin synchronism with said alternating current supply circuit so that anelectrical discharge may be produced successively between said pluralityof stationary electrodes and said collector ring, and means for causinga gaseous fluid to cool said arc, driving it across the faces of saidelectrodes and successively forcing it to transfer from one of saidplurality of electrodes to another.

5. An electric valve of the gas cooled arc type for transmitting energybetween direct and alternating current circuits comprising a pluralityof segmental electrodes and a direct current collector ring soconstructed and arranged as to provide a uniform gap therebetween, meansfor transmitting electrical energy between successive ones of saidplurality of electrodes and said collector ring comprising a conductingmember rotated in said gap in synchronism with said alternating currentcircuit, said member successively reducing the gap between each of saidplurality of electrodes and said collector ring so as to initiate an arcdischarge therebetween and means for causing a gaseous fluid to flowthrough said gap to aid in the transfer of said are discharge from oneof said plurality of electrodes to another.

6. An electric valve of the gas cooled arc type for transmitting energybetween direct and alternating current circuits comprising a pluralityof segmental electrodes and a direct current collector ring soconstructed and arranged as to provide a uniform gap therebetween, meansfor transmitting electrical energy between successive ones of saidplurality of electrodes and said collector ring comprising a memberrotated in said gap in synchronism with said alternating currentcircuit, said member successively reducing the gap between each of saidplurality of electrodes and said collector ring so as to initiate an arcdischarge therebetween, and means for commutating said are dischargebetween said plurality of electrodes.

7. An electric valve of the gas cooled arc type for transmitting energybetween direct and alternating current circuits comprising a pluralityof segmental electrodes mounted within a' casing and insulatedtherefrom, a collector ring mounted within said casing and insulatedtherefrom, said collector ring being so constructed and arranged withrespect to said electrodes as to provide a uniform gap therebetween,means for transmitting electrical energy between successive ones of saidsegmental electrodes and said collector ring comprising a member rotatedwithin said gap in synchronism with said alternating current circuit,said member successively reducing the gap between each of said pluralityof electrodes and said collector ring so as to initiate an arc dischargetherebetween, and means for commutating said arc discharge between saidplurality of electrodesby increasing said are gap when commutation is totake place.

8. An electric valve of the gas cooled arc type for transmitting energybetween direct and alternating current circuits comprising a pluralityof segmental electrodes mounted within a casing and insulated therefrom,a collector ring mounted within said casing and insulated therefrom,said collector ring being so constructed and arranged with respect tosaid electrodes as to provide a uniform gap therebetween, means fortransmitting electrical energy between successive ones of said segmentalelectrodes and said collector ring comprising a member rotated withinsaid gap in synchronism with said alternating current circuit, saidmember successively reducing the gap between each of said plurality ofelectrodes and said collector ring so as to initiate an arc dischargetherebetween, means for commutating said are discharge between saidplurality of electrodes by increasing said are gap when commutation isto take place, and means for producing a flow of gaseous medium forcooling said are discharge and aiding the commutation from one electrodeto another.

9. An electric valve of the gas cooled arc type for transmitting energybetween a direct and an alternating current circuit comprising aplurality of electrodes and a direct current collector ring soconstructed and arranged as to provide a uniform gap therebetween, meansfor' transmitting electrical energy between successive ones of saidplurality of electrodes and said collector ring comprising amember'rotated in said gap in synchronism with the alternating currentof said alternating current circuit, said member successively reducingthe gap between each of said plurality of electrodes and said collectorring so as to initiate an arc discharge therebetween, and a plurality offan blades mounted on said member for producing a flow of fluid mediumto cool said are discharge and cause it to commutate between saidplurality of electrodes.

10. An electric valve of the gas cooled arc type for transmitting energybetween direct and alternating current circuits comprising a pluralityof segmental electrodes mounted within a casing and insulated therefrom,a collector ring mounted within said casing and insulated therefrom,said collector ring being so constructed and arranged with respect tosaid electrodes as to provide a uniform gap therebetween, means fortransmitting electrical energy between successive ones of said segmentalelectrodes and said collector ring comprising a member rotated withinsaid gap in synchronism with said alternating current circuit saidmember successively reducing the gap between each of said plurality ofelectrodes and said collector ring so as successively to initiate an arcdischarge therebetween,

for transmitting energy between a direct and an alternating currentcircuit comprising a plurality of electrodes and a direct currentcollector so constructed and arranged as to provide a uniform gapbetween said electrodes and said collector,

means for transmitting electrical energy between 1 successive ones ofsaid plurality of electrodes and said collector comprising a memberrotated in said gap in synchronism with the alternating current of saidalternating current circuit, said member successively reducing the gapbetween each of said plurality of electrodes and said collector so as toinitiate an electrical discharge therebetween, means for producing aflow of fluid medium to cool said are discharge and cause it tocommutate between said plurality of electrodes, 1;

and heat transfer means in the path of said fluid medium to cool saidfluid medium after it has been heated by said are discharge.

12. An electric valve of the gas cooled arc type for transmitting energybetween direct and alternating current circuits comprising a casing, aplurality of electrodes and a direct current collector insulatinglymounted therein, said collector being so arranged in said casing withrespect to said plurality of electrodes as to provide a uniform gaptherebetween, means for transmitting electrical energy betweensuccessive ones of said electrodes and said collector comprising amember arranged to be rotated within said gap, a synchronous motormounted on said casing drivingly connected to said member and rotatingit within said gap in synchronism with said alternating current circuit,said member successively reducing the gap between each of said pluralityof electrodes and said collector so as to successively initiate an arcdischarge therebetween, and means for commutating said are dischargebetween said plurality of electrodes by increasing said electric gapwhen commutation is to take place.

13, In combination, a supply circuit, a load circuit, one of saidcircuits being an alternating current circuit provided with a pluralityof phase terminals, a converting apparatus interconnecting said phaseterminals and said other circuit,

said converting apparatus comprising a plurality of electrodes mountedin electrically insulated and closely spaced circumferential relationassociated with said phase terminals, other electrode means mounted inspaced relationship with each of said plurality of electrodes so as toprovide a uniform gap therebetween, and means for transmittingelectrical energy between successive ones of said plurality ofelectrodes and said other electrode means comprising a member rotated insaid gap in synchronism with said alternating current circuit, saidmember successively reducing the gap between each of said plurality ofelectrodes and said other electrode means so as to initiate an arcdischarge therebetween, said member being dimensioned to overlapportions of successive ones of said plurality of electrodes as themember is rotated to thereby facilitate the commutation of current fromone of said pluralities of electrodes to the next.

14. An electric valve of the gas cooled arc type for transmitting energybetween a load circuit and a supply circuit, one of said circuits beingan alternating current circuit, comprising a plurality of electrodes anda direct current collector ring so constructed and arranged as toprovide a uniform gap therebetween, and means for transmittingelectrical energy between successive ones of said plurality ofelectrodes and said collector ring comprising a conducting membermounted so as to be relatively rotatable with respect to said pluralityof electrodes, said relative rotation being in synchronism with saidalternating current circuit thereby successively reducing the gapbetween each of said plurality of electrodes and said collector ring toinitiate an arc discharge therebetween and means for directing a flow ofgaseous fluid across said gap for aiding the commutation of said aredischarge from one of said pluralities of electrodes to another as saidconducting member is rotated.

15. In combination, a supply circuit, a load circuit, one of saidcircuits being an alternating current circuit, a transformer and aconverting apparatus interconnecting said circuits, said transformerhaving one Winding connected to said alternating current circuit and aplurality of phase windings inductively associated therewith, saidconverting apparatus comprising a plurality of electrodes associatedwtih said phase windings and mounted in electrically insulated andclosely spaced circumferential relation, other electrode means mountedin spaced relationship with each of said plurality of electrodes so asto provide a uniform gap therebetween, and means for transmittingelectrical energy between successive ones of said plurality ofelectrodes and said other electrode means comprising a conducting membermounted in said gap so as to be relatively rotatable with respect tosaid plurality of electrodes, said relative rotation being insynchronism with said alternating current circuit thereby successivelyreducing the gap between each of said plurality of electrodes and saidother electrode means so as to initiate an arc discharge therebetween,said member having sufficient extent in the direction of rotationthereof to overlap successive ones of said electrodes to therebyfacilitate the commutation of said arc discharge between successiveelectrodes.

ANTHONY J. LARRECQ.

